Process for the recovery of concentrated acetic acid



Jan. l, 1929.

H. SUIDA PROCESS -FOR THERECOVERY OF CONCENTRATED ACETIC ACID FiledMarch 16, 1927 met] mwuo. B002 Eco Mulmsou film hoo ,UNITED STATESPATENT "'oFFlcE.

HERMANN sUmA, on MoDLING, ANEAR VIENNA, AUSTRIA.

IRooEssroR THE RECOVERY oF ooNcnN'rRA'rnn Acnrrc ACID.

Application iled March 16, 192'?, Serial No.'175,832, andvin AustriaJuly 31, 192.6.v

as'the raw material in the processes heretofore 4set forth by theinventor forthe production of concentrated acetic acid, using an`extraction agent which boils at a higher `temperature than acetic acid.The crude pyroligneous acid can be used for these processes only afterthe tai-ry components have been removed therefrom, since otherwise thetai-ry components would pass-into the extraction agent, In carrying outthe said processes the crude pyroligneous acid is freed from a part ofthe tar by being allowed to stand while the remainder (the so-calledsoluble tar) remains behind as a residuewhen the crude vpyroligneousacid is evaporated. Furthermore, the manner in which these processes areperformed requires the employment cfa raw material from which the woodspirit has been removed, that is to say, the wood spirit must firstofall be expelled from the pyroligneous acid. The evaporation of thedilute pyroligneous acid Iand the removal of the have been adopted inthewood-carbonization industry. In the said processes the vapours spirittherefrom require a considerable expenditure of heat which lamounts toalmost two thirds to three quarters of the total'heat expended in theconcentration process according to the above method;

4Recently so-called tar-separating processes leaving the retorts of theWood-carbonizing ovens during the process of carbonizing are l not irstof all condensed and then freed from the tarry constituents, but themixture of hot cases and non-condensable vapours is Itreed rom thetarryconstituents by washing with tar-oils. Consequently tar-free vapoursand.

gases emerge from the tar-separators .of known design, whateverthelrconstruction, which are connected to the ovens or retort's.

' Operation according to the processe's'mentioned at the beginninghereof would, how.-

ever, even in this case, make it necessary that neous acid andwoodspirit vapours is immediately subjected after the tai-ryconstituents have been removed therefrom` in a tar-separator, toextraction by means of an extraction agent. of higher boiling point thanacetic acid, the condensation of the wood-spirit constituents beingeffected only after the acetic acid has been extracted, and the woodgasesalso being separated from the Woodspirit constituents only afterthe extraction of the acetic acid.

The process consists in of wood-gases and of acetic acid, water andwood-spirit vapours coming from .the tar causing the mixture separatorto flow throughV an extraction Y column in which it is 'treated by, forexample, i

spraying with a suitable vextraction agent, for example with cresol. Forthe purpose of better regulating the tem erature of the extractioncolumn it is pre erable-but not absolutely essential-to provide a smallcooling c'oil in the' "upper part of the extraction-- column.v Theacetic acid is completely removed in the extraction column by theextract-ionagent which is still liquid at the ex. traction temperature.The extract, consisting of the extraction agent and concentrated aceticacid, is brought to a suitable degree of concentration by super-heatingin the .lower part-of the extraction column and the extraction agent,charged with a concentrated acetic acid, leaves the apparatus at thelower end, whereupon it is treated as in theV previous processes ,toyield concentrated acetic acid and pure 4extraction agent. The.

water-vapour, practically free from acetic acid, the wood-spirit vapours(which, at the temperature of about prevailing in the column, pass theacetic acid extraction agent unaltered), all of the wood gases and thevapours of any entrained acetic acid extraction agent escape from theupper end of the column. The water vapour and only the ent-rainedvaporous acetic acid extraction agent are condensed in anadjoininf; asuperimposedA condenser l y suitably adjusting the temperature, whereasthe woodspirit vconstituents and the wood gases leave this auxiliaryapparatus at the upper end. The wood spirit constituents (methyl alcoholand acetone) are deposited in a following condenser, which is suppliedwith cold water., whereas the wood-spirit and wood-spirit concomitants(allyl alcohol, al'dehydes, hydrocarbons, etc.) are removed from theywood gases in an adjoining washing tower in known column having mannereither by` water or steam or even by a suitable extraction agent. Themixture of water, free from acetic acid, and suspended and dissolvedacetic acid extraction agent deposited in the first auxiliary column isfreed from the suspended acetic acid extraction agent'by beingv allowedto stand (decantation), the said agentv being returned to the process.The acetic acid extraction agent dissolved in the Water is recovered in'a suito able manner and 1s l also returned to the process.

The material technical progress achieved by the new method of operationresides in the reduction, by utilizing the oven-heat (retort heat), ofthe heat expenditure for the concentration process to about one third toa quarter of the amount used hitherto.

The process will no w be described with reference to the accompanyingdrawing: The gasesand vapours escaping from the retorts or ovens duringthe carbonization enter the tar se arator 2 of any desired constructionat 1 an are lcompletely de-tarred therein by spraying with tar oils ortar. If it is neces.

sary for the com lete de-tarring, a second tar separator may ebroughtinto operation. The completely de-tarred Wood gases, pyroligneous acidvapours and wood-spirit va.- pours leave the tar separator through thepipe 3 and enter the extraction column 4.

' f [he latter is either filled with Raschig l rings or is constructedas a column with intermedate bottoms. The gases and vapours How upwardlyand encounter the liquid extraction agent, for example, cresol, whichenters at 6 through the pipe 5 and is sprayedv downwardly. The agentextracts the acetic acid com letel and asses, charged with concentrateacetic aci into the lower part of the extraction column, which lower I yheated by a steam coil 8. The extract c arged with concentrated aceticacid collects at I and finally flows away. continuously through theswans-neck tube 9. The extract is then conducted, for the purpose ofbeing separated into concentrated acetic acid and 4extraction agent freefrom acetic acid, into a vacuum apparatus. If the thermometer 10indicates a temperature of, for example, 140145, then an extract whichcontains acetic acid of about 90% flows out at 9. The temperatures inthe column 4 aresomewhere above 100. The

temperature' in the column' may be controlled by the small cooling coil11 for the purpose of neutralizing; excess extraction. (condensa- 4tion) heat in certain circumstances, for instance, in the case' ofirregular supply-flow of the gases and vapours from the ovens; lthismeasure is, however, in no way a material feature of the process. Thewood-spirit vaypp'urs, wood-gases and the water va our, free om aceticacid but carrying with t em some entrained extraction agent, emergethrough the pipe12. This mixture passes into the lowart is er port-ionof the column 13-which is provided with a superposed condenser 14. Thesuper'- posed condenser 14 is so adjusted ,by suitable control ofthesupply of water theretov thatl only the water and cresol orthe greaterpart of the water and the total entrainedlcresol are condensed andilowldown through the leave theapparatus with the wood-gases through thepipe 15. Thus there collects at the lower end of the column 13 acompletel de-spirited, acetic acid free condensate whic contains thewhole of the .entrained ext-raction agent; it flows at 16 into'thecondenser pipe 18. The condensate is then separated,

that any small quantities of 'extraction agent (cresol) still dissolvedin the water may be recovered. The wood gases and wood-spirit vapoursemerging throu h the pi 15, being still at a temperature o aboutl0-8()",flow into the upper endzof the tube-condenser 19, in which thewood spirit is in` great part de- 'posited,- andleave the a aratusthrough the separating vessel 20 an t e sWans-neck pipe 21. ,The woodgases pass-through the pipe deca-nting and washing with cold water, intoacetic acid extraction'agent and waterfree from both acetic acid andwood-spirit so 'column 13, while the Wood-spirit constituents `passcompletely through the condenser and A174 and'can flow oil through theswans-neck.

22 into the lower end of the washing tower densable constituents escapethrough the pipe 26.

In the whole rocess heat is only required in a small quantlty at asingle lace, that is in the steam coil 8 at the lower eng of the column4, for the purpose of superheatingthe vapours in the column 4. It ispossible in this manner to obtain in a continuous operation concentratedacetic aci-d, crude wood spirit of. high concentration and wood gasesfree from wood spirit.

What I claim is 1. A process for the recovery of concentrated aceticacid' in the carbonization of 'wood,comprising detarring the mixture ofwood gases, pyroligneous acid vapours and lll Wood-spirit vapours,subjecting the detarred mixture in vapourous or gaseous conditiondirectly Ato extraction with an extraction agent diicultly soluble inwater and having a'boiling point higher than that of acetlc acl toremove the acetic' acid from the mixture and withdrawing the acetic acidin a concentrated state as a liquid with the extraction agent.

p s 5 pyroligneou's acid vapors and wood spirit the wood spiritfr'omth'eremaining mixture 2. A process for the'recovery' ofconcentrathigher'than that of acetic acid to remove the 10 ed aceticacid and Woodspiritinthecarbonizaacetic acid from the mixture,withdrawing tion of Wood, comprising removing the tarry the concentratedacetic' acid` and extractionnstituents from the mlxtureof wood gases,`agent in the form of a liquid, and. separating vapors, subjectingthedetarred mixture in of vapor and gas'. l5

vaporous or gaseous condition directly to ex- In testimony whereof 1have hereunto Aset v tractionwith an extraction agent diicultly my hand.v f .V

soluble in water and having a boiling poi-nt l' -HERMANN .SU1DA.

